Journal of the Optical Society of America B · 1987 · 192 citations · 51 references
Short Wavelength OpticEngineeringLaser ApplicationsAbsorption SpectroscopyHigh-power LasersRadiation GenerationOptical PropertiesPulse PowerOptical PumpingPhotonicsPhysicsWavelength ConversionRare GasLaser DesignTunable Vacuum-ultraviolet/extreme-ultraviolet RadiationSynchrotron RadiationExcimer LasersNatural SciencesSpectroscopyLaser LightApplied PhysicsGas LasersTunable LasersLight AbsorptionConversion Efficiency η
Resonant third‑order sum‑ and difference‑frequency conversion of pulsed‑dye‑laser light in krypton is studied, showing that the conversion efficiency varies with wavelength in a manner consistent with the nonlinear susceptibility and optimal gas pressure. The process uses a 216.6‑nm laser resonant with the Kr two‑photon 4p–5p transition, tuning a second laser between 219–364 nm to generate XUV (72.5–83.5 nm) via sum frequency and between 272–737 nm to produce tunable VUV (127–180 nm) via difference frequency. In the XUV range the efficiency remains nearly constant, yielding pulse powers above 20 W but reduced to ~5 W after absorption, while in the VUV the efficiency rises over an order of magnitude with wavelength, reaching 250 W at 135 nm and 1.8 kW at 175 nm.
Resonant third-order sum- and difference-frequency conversion (ωuv = 2ωR ± ωT) of pulsed-dye-laser radiation is investigated in the rare gas, Kr. The frequency ωR(λR = 216.6 nm) is resonant with the Kr two-photon transition 4p–5p[5/2, 2]. On tuning ωT in the range λT = 219–364 nm, the sum frequency generates light in the extreme ultraviolet (XUV) (λxuv = 72.5–83.5 nm). In agreement with theoretical predictions, the conversion efficiency η is almost constant within this spectral range. At input powers PR = 14 kW and PT = 400 kW, the pulse power of the XUV exceeded Pxuv = 20 W. However, absorptions in the Kr gas reduced the power of the detected XUV light to about 5 W (effective efficiency, η = 1.2 × 10−5). With laser light at λT = 272–737 nm, the difference frequency generates continuously tunable radiation in the vacuum ultraviolet (VUV) (λvuv = 127–180 nm). In this range, the conversion efficiency increases with wavelength by more than 1 order of magnitude. At λvuv = 135 nm, for example, input powers PR = 0.2 MW and PT = 1.2 MW generate VUV light with Pvuv = 250 W (n = 1.8 × 10−4). At λvuv = 175 nm, a lower input (PR = 80 kW, PT = 560 kW) produced VUV light pulses of Pvuv = 1.8 kW (η = 2.8 × 10−3). This spectral variation of η is in agreement with the calculated wavelength dependence of the nonlinear susceptibility and of the gas pressure required for optimum VUV output.
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